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NOVEMBER 04 - WIND UPLIFT - CHECK THE SMALL PRINT TO AVOID CLAIMS

Wind damage to roofs could be costing the British economy up to £800+million*- and set to rise with wind speeds increasing through climate change. But some part of that could be avoided, claims Glidevale Ltd.

The company, one of the leading suppliers of roofing underlays, is concerned at the lack of awareness regarding the role of underlays in resisting wind uplift loads on roofs. BS5534: 2003 Code of Practice for Slating and Tiling requires that underlays be able to resist 2/3rds of the total load at the specified batten gauge with 1/3rd absorbed by the roof covering. Most reputable roof covering manufacturers provide fixing specifications for their products but all assume that the underlay will resist the loads described above. If the underlays cannot resist the wind uplift loads it may well contribute to the removal of tiles in exposed areas or in storm conditions.

Glidevale has commissioned an independent report, “Wind Uplift on Roofing Underlays”, which examines geographical, altitude and climatic conditions round the UK and wind loading calculations. It clearly shows that for buildings of two or three storeys, a windload resistance of at least 2.5kPa is required at maximum batten gauge to ensure the underlay can be safely used at more than 95% of UK locations.

Neil Rideout, Glidevale Technical Director, comments, “Many independent certificates make a statement that a product may be considered equal in strength to Type 1F. Yet they quote actual resistance to wind load figures within performance tables which show that the products are anything but equal in strength to Type 1F and have severe restrictions on use.

“There is a danger that specifiers and contractors accept that all modern lightweight alternatives to Type 1F are equal in all respects, on the basis the products are certified. Many are not aware how important the underlay is in terms of wind uplift and do not read the small print. This is becoming an issue of concern, among the insurance industry and building/roofing organisations. Weather related insurance claims in the UK averaged out at £825million pa, with the majority of this being wind related with an average 200,000 buildings damaged by high winds in the UK every year. The damage may be the result of tiles not being correctly fixed, but it may also be due to the underlay deflecting under load to such a degree it dislodges the slates and tiles because the underlay has been used outside of its restrictions as quoted in independent certification. Insurance claims affect all of us inevitably leading to an increase in premiums. Results from the UK Climate Impacts Programme predict wind speeds increasing by up to 6%, so the problem will only get worse unless heed is paid to the small print of certification.”

Glidevale’s Protect A1 impermeable and Protect VP400 vapour permeable underlays both have independent certification allowing unrestricted use with regard to wind uplift, meeting the 2.5kPa performance criteria. Copies of the “Wind Uplift on Roofing Underlays” report are available from Glidevale, 2 Brooklands Road, Sale M33 3SS, email info@glidevale.com.

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